Meet the Instructors

Antoine Flahault

Professor of Public Health and Director of the Institute of Global Health (Faculty of Medicine, University of Geneva) and co-Director of Centre Virchow-Villermé (Université Paris Descartes)University of Geneva and Université Paris Descartes – Sorbonne Paris Cité

Rafael Ruiz De Castañeda

Institute of Global Health - Faculty of MedicineUniversity of Geneva

Defeating Ebola Together Week 1: Understanding the Disease
"Epidemiology of the Ebola Disease in West Africa"

Dear viewers: today, I'd like to

tell you about my own experience with the Ebola disease,

and I'd like to comment on the

current Ebola epidemic as it stands today, on December 15th, 2014.

The disease known as Ebola first appeared in 1976,

in what was formerly Zaire, today known as the Democratic Republic of the Congo.

The disease's virus is a filovirus that looks like a piece of string.

But today, we're not going to talk about virology or molecular biology, but rather about

Ebola's epidemiological and ecological aspects in West Africa.

We'll also talk about the importance of an integrated approach, known as

One Health, or an ecological approach referred to as

the "ecohealth" approach for the prevention and long-term fight against the disease.

I worked in West Africa for eight years.

From 1994 to 1998, I ran the Swiss scientific research center there.

During this period, we were conducting major research projects in parasitology, forest botany,

as well as on the behavior of monkeys, including chimpanzees.

In November of 1994, we witnessed a sudden rise in mortality within our group of chimpanzees, eight of whom died.

I immediately thought it was the Marburg virus and I strictly prohibited

our researchers from touching the dead bodies, because these researchers were

behaviorists, not microbiologists.

One of the researchers nonetheless opened up one of the bodies and

subsequently became ill. He had to be hospitalized in Abidjan.

The doctors starting by treating him for malaria, which they followed with a course of antibiotics,

before once again administering treatment for malaria.

At that point, we transported the patient to Switzerland, where, thankfully, he recovered.

It was then that Dr. Leguénon, of the Pasteur Institute in Paris, identified the disease as the Ebola virus.

Which means we were all very lucky.

It seems that the virus was much less pathogenic than the strains

we know of today in Central Africa,

and than the strain currently circulating in West Africa.

So I almost inadvertently prevented a discovery, had the researchers followed my instructions...

Thankfully, the researcher survived, and we are certainly very happy things turned out that way.

Afterwards, Dr. Formenty started studying the disease's reservoir

and conducted a search among numerous other species in Taï National Park.

Unfortunately, he was unable to find any other carriers of the virus.

He came to the conclusion that the chimpanzee could not be a reservoir host.

Other research has demonstrated that

traces of the virus can be found in bats,

fruit-eating bats such as the Hypsignathus and Epomops species.

Today, we know that there is a threefold cycle.

The virus' reservoir is in all likelihood to be found in fruit bats, who transmit the virus among themselves, probably without getting sick.

Occasionally, they may transmit the virus to wild animals, such as duikers (small antelopes) and chimpanzees,

but they can also transmit it to humans.

In Taï National Park, we learned that the virus is very easily transmitted among chimpanzees, and they die from it.

That's why we suspect that many wild animals are occasional hosts, what we call "spillover hosts," but not reservoir hosts per se.

However, when the virus is transmitted to humans, it spreads very quickly among us,

which is what we are seeing today with the epidemic in West Africa.

But that's not the end of the story.

Knowing which species were concerned, we needed to determine

the socio-ecological conditions on the basis of which these diseases can emerge.

In trying to answer this question, we observed that an agricultural transformation had taken place,

from subsistence farming to industrial farming.

Farmers who were accustomed to managing their own plantations

all of a sudden found themselves faced with a new system of industrial agriculture, and many lost their land.

They were left with little choice but to be hired by these industrial farms in order to make a living.

Many became palm fruit pickers, or pickers of some other fruit,

and were thus exposed to bats,

much more so than they otherwise would have.

We also need to recognize the impact of this ecological change on the

bats themselves, who often don't know where they are

or where to find a dwelling, and have to search for types of trees or ecosystems to which they can successfully adapt.

This is probably how humans and the disease's reservoir hosts came together.

There remains much research to do in this area. We are far from knowing all the details.

The other major factor, of course, has been the

inadequacy of local healthcare systems, which has allowed

the disease to spread quickly, compounded by the

high level of mobility of the local populations, as well as their cultural practices.

So we are dealing with two phenomena:

1) the emergence of the disease, which is

really an ecological and social phenomenon, and 2) the rapid transmission